<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>position1</title>
    <style>
        body {
            height: 3000px;
        }
        div {
            width: 100px;
            height: 100px;
            background-color: red;
            position: fixed;
            right: 0;
            bottom: 0;
        }
    </style>
</head>
<body>
    <div>返回顶部</div>
</body>
</html>